Well I have found another useful bit of information hidden deep within the bowels of the ESX configuration. Stumbled across /proc/vmware/pci while trying to track down a flaky hba using the command below.

cat /proc/vmware/pci | grep vmhba

Well change this to…

cat /proc/vmware/pci | grep vmnic

… and you get a nice clean list of your network adapters, minus hardware addreseses.

Looking at the list above I can quickly see which two nics are my onboard Broadcoms (on my HP DL380g5). Now I can isolate vmnic1 from vmnic2 using the ethtool command to make the lights on each port blink on and off. In the example below I will make vmnic1 blink for 20 seconds.

ethtool -p vmnic1 20

Note that I have not found it particularly easy to identify which port is blinking, due to the fact that all my ports are binking in one way or another. I recommend getting a good look at the ports before you run ethtool, and then run it and look again. The comparison makes it easier to identify said port.